Injection nozzles are used to inject extrudate from an extruder screw or an injection screw prior to further processing. Such further processing might include extrusion through a die to produce a continuos extruded shape or injection into an injection mold to produce a molded part.
In order to reduce inventory costs, operators often feed standard, uncolored thermoplastic pellets and colored pigments into an extrusion or an injection machine to produce colored plastic products. Other additives may be added to thermoplastic for a variety of purposes. Such additives might include glass fibers, glass beads, steel powder, calcium and even animal fat. It is usually important to the quality of the resulting product that these additives are evenly mixed with the thermoplastic. It is also important that resulting mixture be uniform, isothermal and relatively free of material degradation.
Operators who produce a wide variety of products often employ machines having standard injection or extrusion barrels and screws capable of processing a wide variety of thermoplastic materials. Such standard equipment is often not well adapted for optimally mixing a particular thermoplastic material and a pigment to produce an evenly colored product. Inadequate mixing causes streaks in the product due to contrasting areas have heavy and light pigment. Often excess amounts of costly pigment are used to compensate for inadequate mixing. Consequently, there is often a need for a mixing nozzle which can be mounted to an extrusion or injection machine that will receive molten thermoplastic material and pigment from the extrusion or injection machine and mix the thermoplastic and the pigment more completely prior to further processing. Still further, since excessive shear and compression of an extrudate can elevate the temperature of the extrudate and degrade its material properties, there is a need for a mixing nozzle that mixes extrudate thoroughly while subjecting it to minimum amounts of heat producing shear and compression.